1. Field of the Invention
This invention relates in general to the field of lightweight wall curtains for multi-story buildings and, particularly, to the construction and mounting of individual wall curtain panels on the framework of a building to sheath the building framework and to provide finished, decorative, and waterproof building exterior walls.
2. Description of the Prior Art
Various materials are used to sheath building frames, such as stone, including granite and marble, ceramic tile, glass and metal sheet or plate. Such materials as marble are cut to uniform size and are bonded to metal backing plates. The metal backing plates are then fastened to building frame members to provide an exterior cover for the building.
This method of sheathing buildings is unsatisfactory in that solid slabs, such as granite, marble, or the like, bonded to steel backing plates remarkably increase the weight of the building, and the rigidity of the slabs renders the building walls vulnerable to cracking when subjected to earthquake tremors. Further, the coefficient of expansion for marble, for instance, is different from the coefficient of expansion of steel backing plate. Therefore, as the temperature of the marble and of the steel changes, there is danger of the entire panel warping due to differential expansion and contraction of the two bonded materials. A warped panel can cause the marble or like material to crack; it can cause the sealant between panels to become dislodged; and it can cause leaking between panels. Dislodged sealant has also been known to leach over the exterior face of the panel, thereby spoiling the general appearance of the building. The modulus of heat conductivity and coefficient of expansion of steel backing plates are both high, and it is difficult to effectively insulate steel backing plates when bonded to the exterior facing material.